sum of particular objects values in an array code example

Example 1: javascript sum array values by key

var array = [
  {name: "Peter", age: 43},
  {name: "John", age: 32},
  {name: "Jake", age: 21}
];

array.reduce(function(sum, current) {
  return sum + current.age;
}, 0); // 43 + 32 + 21 = 96

Example 2: javascript sum array of objects

arr = [{x:1}, {x:3}]

arr.reduce((accumulator, current) => accumulator + current.x, 0);